My Russian is effectively non-existent. However this looks to be an impressive valve: only 330mA for the heater, yet 7.5W Pa max. I note with interest that there are the usual rather wide tolerances for emission and gm, with which we are familiar from our experiences with 6C45P! Best to bet on them generally making the lower end...

Originally posted by 7N7 Best to bet on them generally making the lower end...

7N7

Probably true. A cursory look suggests that the 6J52P is similar to the 7788 in the key specs. The 6J52P is specified to have a gm value of 55mA/V at 42mA, while the 7788 is spec'd at 50mA/V at 35mA. These values are within the tolerance range of each other, especially if both tubes were run at the same plate current. Given the occasionally optimistic nature of Russian tube data sheets, it's hard to make the conclusion that on is "better" than the other, whatever "better" means.

I've never touched a 6J52P, but I think it would be worthwhile looking into it.

Probably true. A cursory look suggests that the 6J52P is similar to the 7788 in the key specs. The 6J52P is specified to have a gm value of 55mA/V at 42mA, while the 7788 is spec'd at 50mA/V at 35mA. These values are within the tolerance range of each other, especially if both tubes were run at the same plate current. Given the occasionally optimistic nature of Russian tube data sheets, it's hard to make the conclusion that on is "better" than the other, whatever "better" means.

I've never touched a 6J52P, but I think it would be worthwhile looking into it.

Absolutely.

Every E810F (7788) I ever tested made its specified gm, whereas the 6C45Ps were all over the place.

Seeing the Russian tubes going cheap on ePay I bought and tested some ‘standard’ ones as the 6P15P-ev and the 6N6P in existing circuits. As experience was positive I went chasing the high GM ones. It was not hard to find the E180F, the E280F, 437, 417 ‘clones’, all selling for very modest prices: the Russian sellers are kind enough to state the western equivalents in their listings, once in a while they rather mention E180F in the title instead of 6J9P. Anyway, I never found any offering a E810F or a D3A, so I went looking for their ‘clones’ on google, and found references towards the already mentioned 6J52P (also called 6sh52P or 6zh52p – in Cyrillic it is a kind of X) and the 6P38P, this one reaching (on datasheet) values above the 60ma/V. Still I have not found any ePay seller with these tubes.